NAME
fns_dns − overview of FNS over DNS implementation
DESCRIPTION
Federated Naming Service (FNS) provides a method for federating multiple naming services under a single, simple interface for the basic naming operations. One of the naming services supported by FNS is the Internet Domain Name System, or DNS (see in.named(1M)). DNS is a hierarchical collection of name servers that provide the Internet community with host and domain name resolution. FNS uses DNS to name entities globally. Names can be constructed for any enterprise that is accessible on the Internet; consequently, names can also be constructed for objects exported by these enterprises.
FNS provides the XFN interface for performing naming resolution on DNS domains and hosts. In addition, enterprise namespaces such as those served by NIS+ and NIS can be federated with DNS by adding TXT records to DNS. To federate an NIS+ or NIS namespace under DNS, you first obtain the root reference for the NIS+ hierarchy or NIS domain. This reference is referred to as the next naming system reference because it refers to the next naming system beneath the DNS domain. This reference contains information about how to communicate with the NIS+ or NIS servers and has the following format:
<domainname> <server name> [ <server address> ]
where <domainname> is the fully qualified domain name. Notice that NIS+ and NIS have slightly different syntaxes for domain names. For NIS+, the fully qualified domain name is case-insensitive and terminated by a dot character (’.’). For NIS, the fully qualified domain name is case-sensitive and is not terminated by a dot character. For both NIS+ and NIS, <server address> is optional. If it is not supplied, a host name lookup will be performed to get the machine’s address.
For example, if the machine wiz-nisplus-server with address 133.33.33.33 serves the NIS+ domain wiz.com., the reference would look like this:
wiz.com. wiz-nisplus-server 133.33.33.33
For NIS, the reference information is of the form:
<domainname> <server name>
For example, if the machine woz-nis-server serves the NIS domain Woz.COM, the reference would look like this:
Woz.COM woz-nis-server
After obtaining this information, you then edit the DNS table (see in.named(1M)) and add a TXT record with this reference information. The TXT record must be associated with a DNS domain that includes an NIS record. For example, the reference information shown in the examples above would be entered as follows.
For NIS+:
TXT "XFNNISPLUS wiz.com. wiz-nisplus-server 133.33.33.33"
For NIS:
TXT "XFNNIS woz.com woz-nis-server"
Note the mandatory double quotes (’"’) delimiting the contents of the TXT record. After making any changes to the DNS table, you must notify the server by either restarting it or sending it a signal to reread the table:
#kill -HUP ’cat /etc/named.pid’
This update effectively adds the next naming system reference to DNS. You can look up this reference using fnlookup(1) to see if the information has been added properly. For example, the following command looks up the next naming system reference of the DNS domain Wiz.COM:
#fnlookup -v .../Wiz.COM/
Note the mandatory trailing slash (’/’).
After this administrative step has been taken, clients outside of the NIS+ hierarchy or NIS domain can access and perform operations on the contexts in the NIS+ hierarchy or NIS domain. Foreign NIS+ clients access the hierarchy as unauthenticated NIS+ clients. Continuing the example above, and assuming that NIS+ is federated underneath the DNS domain Wiz.COM, you can now list the root of the NIS+ enterprise using the command:
#fnlist .../Wiz.COM/
SEE ALSO
fnlist(1), fnlookup(1), nis+(1), in.named(1M), ypserv(1M), xfn(3XFN), fns(5), fns_nis(5), fns_nis+(5), fns_references(5), fns_x500(5)